Biaxially oriented polypropylene-based resin film and package using same

Abstract

The invention provides a biaxially oriented polypropylene-based resin film having a base layer (A) consisting of a polypropylene-based resin composition and surface layers (B) consisting of a polypropylene-based resin composition on both sides of base layer (A), wherein the film has a) a mesopentad fraction of the polypropylene-based resin composition constituting base layer (A) of 95.0 to 99.5%; b) a ratio of α-olefin monomer-derived component to a total of propylene monomer-derived component and α-olefin monomer-derived component in the polypropylene-based resin composition constituting base layer (A) of 0.2% by mole or less; c) a ratio of butene-1 monomer-derived component to a total of propylene monomer-derived component and α-olefin monomer-derived component in the polypropylene-based resin composition constituting surface layers (B) of 5 to 10% by mole; and d) a thickness of 60 μm or less, wherein the thickness of surface layers (B) is 3-10% of the total layer thickness of the film.

1 . A biaxially oriented polypropylene-based resin film, comprising:
 a base layer (A) consisting of a polypropylene-based resin composition; and   surface layers (B) consisting of a polypropylene-based resin composition on both sides of the base layer (A),   the biaxially oriented polypropylene-based resin film satisfying the following a) to d):   a) a mesopentad fraction of the whole polypropylene-based resin composition constituting the base layer (A) of 95.0% or more and 99.5% or less;   b) a ratio of an α-olefin monomer-derived component to a total of a propylene monomer-derived component and the α-olefin monomer-derived component in the whole polypropylene-based resin composition constituting the base layer (A) of 0.2% by mole or less;   c) a ratio of a butene-1 monomer-derived component to a total of a propylene monomer-derived component and an α-olefin monomer-derived component in the polypropylene-based resin composition constituting the surface layers (B) of 5% by mole or more and 10% by mole or less; and   d) a thickness of the biaxially oriented polypropylene-based resin film of 60 μm or less, and a ratio of a thickness of the surface layers (B) to the total layer thickness of the biaxially oriented polypropylene-based resin film of 3% or more and 10% or less.   
     
     
         2 . A biaxially oriented polypropylene-based resin film, comprising:
 a base layer (A) consisting of a polypropylene-based resin composition; and   surface layers (B) consisting of a polypropylene-based resin composition on both sides of the base layer (A),   the biaxially oriented polypropylene-based resin film satisfying the following A) to D):   (A) a melting point peak temperature of a polypropylene-based resin having the lowest DSC melting point in the polypropylene-based resin composition constituting the base layer (A) of 160° C. or higher;   (B) a ratio of an α-olefin monomer-derived component to a total of a propylene monomer-derived component and the α-olefin monomer-derived component in the whole polypropylene-based resin composition constituting the base layer (A) of 0.2% by mole or less;   (C) a ratio of a butene-1 monomer-derived component to a total of a propylene monomer-derived component and an α-olefin monomer-derived component in the polypropylene-based resin composition constituting the surface layers (B) of 5% by mole or more and 10% by mole or less; and   (D) a thickness of the biaxially oriented polypropylene-based resin film of 60 μm or less, and a ratio of a thickness of the surface layers (B) to the total layer thickness of the biaxially oriented polypropylene-based resin film of 3% or more and 10% or less.   
     
     
         3 . The biaxially oriented polypropylene-based resin film according to  claim 1 , wherein a melt flow rate (MFR) of the whole polypropylene-based resin composition constituting the base layer (A) is 2.0 g/10 min or more and 4.5 g/10 min or less. 
     
     
         4 . The biaxially oriented polypropylene-based resin film according to  claim 1 , wherein the polypropylene-based resin composition constituting the base layer (A) includes two or more polypropylene homopolymers; a polypropylene homopolymer having the highest mesopentad fraction among the polypropylene homopolymers has a mesopentad fraction of 97.5% or more; and a polypropylene homopolymer having the lowest mesopentad fraction among the polypropylene homopolymers has a mesopentad fraction of 96.5% or less. 
     
     
         5 . The biaxially oriented polypropylene-based resin film according to  claim 1 , wherein the polypropylene-based resin composition constituting the base layer (A) includes at least one kind of polymer selected from the group consisting of propylene homopolymer, propylene-ethylene copolymer, propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer, and propylene-pentene-1 copolymer. 
     
     
         6 . The biaxially oriented polypropylene-based resin film according to  claim 1 , having a Young's modulus in a longitudinal direction of 2.0 GPa or more, and a Young's modulus in a width direction of 4.0 GPa or more. 
     
     
         7 . The biaxially oriented polypropylene-based resin film according to  claim 1 , having a melt cut seal strength of 18 N/15 mm or more. 
     
     
         8 . The biaxially oriented polypropylene-based resin film according to  claim 1 , having a heat seal attainable strength of 3 N/15 mm or more. 
     
     
         9 . A package comprising the biaxially oriented polypropylene-based resin film according to  claim 1 . 
     
     
         10 . The biaxially oriented polypropylene-based resin film according to  claim 2 , wherein a melt flow rate (MFR) of the whole polypropylene-based resin composition constituting the base layer (A) is 2.0 g/10 min or more and 4.5 g/10 min or less. 
     
     
         11 . The biaxially oriented polypropylene-based resin film according to  claim 2 , wherein the polypropylene-based resin composition constituting the base layer (A) includes two or more polypropylene homopolymers; a polypropylene homopolymer having the highest mesopentad fraction among the polypropylene homopolymers has a mesopentad fraction of 97.5% or more; and a polypropylene homopolymer having the lowest mesopentad fraction among the polypropylene homopolymers has a mesopentad fraction of 96.5% or less. 
     
     
         12 . The biaxially oriented polypropylene-based resin film according to  claim 2 , wherein the polypropylene-based resin composition constituting the base layer (A) includes at least one kind of polymer selected from the group consisting of propylene homopolymer, propylene-ethylene copolymer, propyelen-butene-1 copolymer, propylene-ethylene-butene-1 copolymer, and propylene-pentene-1 copolymer. 
     
     
         13 . The biaxially oriented polypropylene-based resin film according to  claim 2 , having a Young's modulus in a longitudinal direction of 2.0 GPa or more, and a Young's modulus in a width direction of 4.0 GPa or more. 
     
     
         14 . The biaxially oriented polypropylene-based resin film according to  claim 2 , having a melt cut seal strength of 18 N/15 mm or more. 
     
     
         15 . The biaxially oriented polypropylene-based resin film according to  claim 2 , having a heat seal reaching strength of 3 N/15 mm or more. 
     
     
         16 . A package comprising the biaxially oriented polypropylene-based resin film according to  claim 2 .